I went through this similar question at https://stackoverflow.com/a/7410228/880040 and the 6th thing to check,
Make that your terminal capabilities file exists:
ls -lh /usr/share/terminfo/*/$TERM
Is what doesn't pass. This entire folder is empty. tmux works as expected when starting it from a ssh session. On the tty session, it just hangs on a newline after the tmux command. Cannot kill it with ctrl-c either, have to ssh in and killall tmux.
$TERM is 'linux' OS is Ubuntu 11.10 (server edition) 32 bit
Unfortunately the above post did not explain what to do if /usr/share/terminfo was empty.